This invention relates to polyolefin compositions and, more particularly, to polyolefin compositions which can be used to produce fibers and related filamentous structures which are readily dyed by conventional dying techniques, and to films having improved dyeability and printability.
Polyolefins, and more particularly, polypropylene have found wide spread use in the production of films and fibers.
Fibers and films of polypropylene, both homopolymers and copolymers, are well known. However, these fibers have proven to be exceedingly difficult to dye with common dyes, especially from an aqueous bath. This serious disadvantage has severely restricted the use of polypropylene.
Suggestions have been made in the art to improve the dyeability of polypropylene. For example, graft polymerization to the polyolefin with dye-receptive comonomers has been suggested, but this often effects the spinnability of the copolymer and has not been widely adopted. Attempts also have been made to improve the dyeability of polyolefins by blending the polyolefin with other materials such as polyurethanes, polyamides and epoxy resins. Generally, these procedures result in moderate improvements of the dyeability, but the improvements are offset by other problems such as poor compatibility resulting in generally unacceptable product uniformity. U.S. Pat. No. 3,402,222 describes a polypropylene composition whose dyeing characteristics have been improved by mixing a polypropylene with a copolymer of an alkoxy ethyl acrylate and certain polar comonomers such as, for example, sodium 2-acrylamido-2-methyl propane sulfonate.
British Pat. No. 995,802 describes compositions of polyolefins having improved dyeability, and these compositions comprise blends of (1) a solid homopolymer or copolymer of a mono alphaolefin and (2) a copolymer of a major amount of interpolymerized ethylene and a minor amount of certain specified comonomers such as N-vinyl pyrrolidones, N-vinyl succinimides, acrylamides, acrylic acids and esters, vinyl sulfonic acids, vinyl esters (e.g., vinyl propionate) and dialkylvinyl phosphine oxides.
In spite of the suggestions made in the prior art, the generally recognized commercial method for coloring polypropylene fibers is spin coloration with pigments. The most important pigments are the organic pigments although titanium dioxide and carbon blacks also are used.
Although improvements have been made in the dyeability of polyolefins such as polypropylene, the dyeability characteristics have not been entirely satisfactory in depth of shade or fastness properties. Also, films from the polypropylene resins have been found to be difficult to print on, and expensive and time-consuming procedures such as flame treatment or radiation have been employed to improve printability properties of such films.